The present invention concerns a force detection device, and particularly concerns a force detection device suited for detecting forces applied in predetermined coordinate axis directions and moments applied around predetermined coordinate axes.
Various types of force detection devices are utilized for controlling the motions of robots and industrial machines. Compact force detection devices are also incorporated as man-machine interfaces of input devices for electronic equipment. In order to achieve a compact size and cost reductions, a force detection device that is used in such an application is required to be as simple in structure as possible and yet enable forces of the respective coordinate axes in three-dimensional space to be detected independent of each other.
Generally, detection targets of a force detection device are force components in predetermined coordinate axis directions and moment components around predetermined coordinate axes. When an XYZ three-dimensional coordinate system is defined in a three-dimensional space, detection targets are six components of force components Fx, Fy, and Fz in the respective coordinate axis directions, and moment components Mx, My, and Mz around the respective coordinate axes.
As a force detection device capable of detecting such six force components independent of each other, for example, a device with a comparatively simple structure is disclosed in U.S. Pat. No. 6,915,709. In this device, a structural member including two substrates connected by a plurality of columnar members is prepared, and in a state where one of the substrates is fixed, when a force is applied to the other, by measuring displacements of the columnar members individually, components of the applied force are detected.
U.S. Pat. No. 7,219,561 discloses a technique which simplifies arithmetic operation for detecting components of an applied force by providing a wiring between specific electrodes of capacitance elements by using the capacitance elements as sensors for measuring displacements of the columnar members individually.
In the force detection devices disclosed in the above-described Patent Documents, inclinations of the respective columnar members are obtained independent of each other, and based on the inclination form of the plurality of columnar members, six force components are detected independent of each other. Therefore, sensors for measuring the inclination degrees of the respective columnar members independent of each other are necessary. Particularly, in a device having a function of detecting six force components, a plurality of columnar members parallel to the Z-axis direction are disposed on a substrate parallel to an XY plane, and sensors which measure the inclination degrees with respect to the X-axis direction and the inclination degrees with respect to the Y-axis direction of the respective columnar members independent of each other are necessary, and the structure of the whole device inevitably becomes complicated.
For example, as illustrated in the above-described Patent Documents, when a sensor using capacitance elements is utilized as a sensor for measuring an inclination degree, in order to measure both an inclination degree with respect to the X-axis direction and an inclination degree with respect to the Y-axis direction of one columnar member, capacitance elements must be disposed in the positive direction and the negative direction of the X-axis and in the positive direction and the negative direction of the Y-axis. In a device thus requiring many capacitance elements, the wiring is also inevitably complicated, and the structure of the whole device becomes complicated and the manufacturing cost increases.